[OPy][BF4] Selective Extraction for Trace Hg2+ Detection by Electrochemistry: Enrichment, Release and Sensing

Trace mercury ion (Hg2+) detection is important for environmental monitoring and water safety. In this work, we study the electrochemical strategy to detect trace Hg2+based on the preconcentration of temperature-controlled N-octylpyridinium tetrafluoroborate ([OPy][BF4]) dispersive liquid–liquid microextraction. The [OPy][BF4] selectively extracted Hg2+from aqueous solution by the adsorption of unsaturated N in [OPy][BF4], which increased the concentration of Hg2+and decreased that of other interference ions. It was noted that the adsorption of [OPy][BF4] to Hg2+was weakened by aqueous solution. Hence, after extraction, precipitated [OPy][BF4] was diluted by a buffer solution comprising a mixture of water and acetonitrile to release Hg2+and the single was detected by electrochemistry. Water is proposed to release Hg2+adsorbed by [OPy][BF4], and the acetonitrile serves as a co-solvent in buffer solution. Sensitivity and anti-inference ability of sensors were improved using the proposed method and Hg2+releasing procedure. The detection limit (S/N = 3) of the sensor is 0.0315μg/L with a linear range from 0.1 to 1μg/L. And the sensor exhibits good recovery with an range from 106 % to 118%, which has great potential for trace Hg2+determination.Keywords:mercury ions detection;electrochemical sensor;ionic liquid;liquid–liquid extraction